Adaptive threshold technique for detecting reel-to-bedknife contact

ABSTRACT

A control system for a cutting reel unit includes a height-of-cut adjusting system and a reel-to-bedknife clearance adjusting system. The height-of-cut adjusting system includes a first frame; a second frame; a cutting reel supported by the second frame; a bedknife arranged adjacent to the cutting reel and supported by the second frame; at least one support element arranged to translate along the ground and arranged to support the first frame; and at least one first actuator connected between the first frame and the second frame and arranged to adjust the relative elevation of the second frame with respect to the first frame. The reel-to-bedknife clearance adjusting system includes at least one second actuator operatively connected between the reel and the second frame and a sound detector. An adaptive threshold technique may be used for detecting reel-to-bedknife contact during a pre-adjustment analysis. The adaptive threshold technique may include sampling each detector and analyzing the detector signal, setting detection threshold levels based on the average, maximum and minimum levels in the absence of reel-to-bedknife contact, and detecting contact between the reel and bedknife by determining if the detector signal is outside a detection threshold window.

TECHNICAL FIELD OF THE INVENTION

The invention relates to cutting reel units for mowers, and particularlysystems-based mechanisms and methods for adjusting cutting reel units.

BACKGROUND OF THE INVENTION

Conventional mowing machines have an attached cutting reel unit ormultiple units. Such machines typically move the cutting reel unitacross the ground adjacent to the machine. Grass beneath the cuttingreel unit is mowed as the machine travels forward. Conventional reelmower vehicles can include a plurality of arm members that extend fromthe vehicle, each arm having a cutting reel unit attached to its outerend portion.

The cutting reel units typically include front and rear skids or rollersthat support or carry the cutting reel unit across the surface of theground during mowing operation. Such vehicles and cutting reel units aredisclosed for example in U.S. Pat. Nos. 5,343,680; 5,412,931 and5,459,984.

Conventional cutting reel units provide a plurality of blades coupledtogether to form a generally cylindrical reel that rotates about atransverse axis. The blades pass in close proximity to a bedknife tocreate a scissoring action for cutting vegetation such as grass. A frametypically houses the reel and bedknife. Wheels, rollers or skids arecoupled to the frame for engaging or rolling across the ground tooperatively support the reel and bedknife at a predetermined heightabove the ground. The height at which grass is cut is thereforedetermined by the height at which the wheels, rollers or skids carry aframe, reel and bedknife above the ground. Cutting reel units aretypically used for mowing golf courses or other areas were a relativelylow and accurate cut is desirable.

To produce a high quality cut, and a cut that is even for multiplecutting reel units and across mowing passes by a machine with multiplecutting reel units, it is necessary that the height-of-cut for eachcutting reel unit be properly adjusted. It is known that reel mowershave an adjustment mechanism for adjusting the reel mowing height. Onetype of height adjustment mechanism utilizes a plurality of verticallyaligned holes for a cutting unit frame. The rollers are coupled to amounting member or plate that includes an opening. The mounting plate iscoupled to the frame by insertion of a pin through both the mountingplate opening and one of the holes defined by the cutting unit frame.The cutting height can be varied by inserting the pin through adifferent hole in the frame. Other types of height adjustment mechanismsutilize threaded bolts which set the adjustment height using nutsengaged on the bolts and positionable to support a portion of the framesuch that the cutting reel unit is held securely in the desired verticalposition with respect to the rollers. A wrench is used to adjust thenuts to positions on the bolts to thereby adjust the cutting height.

Another type of cutting reel unit utilizes a slotted mounting arm thatis coupled with the rollers. A bolt received by the slot is used toadjust the height by loosening the bolt and shifting the slide-mountingarm to a new position.

For all height-of-cut adjustments, there is a generally accepted andcommon method for determining a cutting reel unit's existingheight-of-cut and how far it needs to be adjusted towards a targetedadjustment. The procedure for setting the cutting height typicallyinvolves fastening a gauge bar to the bedknife such that the uppersurface of the bar is parallel to a forward, horizontal position of thebedknife and at the desired distance below the cutting edge of thebedknife. The front and rear rollers are then adjusted to come intocontact with the upper surface of the gauge bar.

The adjustment relationship between the front and rear rollers—relativeto the cutting reel itself—is often termed the ‘angle of attack’ for thebedknife. This relationship refers to the relative pitch (front to back)or angle of the bedknife in relation to the ground surface. The angle ofbedknife attack is an important parameter which affects the cut qualityand effectiveness. Varying the height-of-cut must take the angle ofattack into consideration.

Cutting reel units cut properly only if the reel-to-bedknife clearanceis properly adjusted. Currently, the reel-to-bedknife clearance ismanually adjusted. The adjustment is made on a regular basis, typicallybefore use, or made during or after use when poor cut quality isdetected. Sometimes the adjustment is made such that the reel touchesthe bedknife and then the reel and bedknife are allowed to wear intoplace. Adjustments are also made after repair or replacement of the reelor bedknife.

Specifically, the reel-to-bedknife clearance is adjusted by moving thereel away from the bedknife to allow a specific gap—that is even acrossthe length of the reel and bedknife—between both the reel and bedknife.The gap is then measured by inserting a feeler gauge (of the samethickness as the adjustment gap) between the reel and bedknife. Theadjusted gap between the reel and bedknife is determined to be accuratewhen the feeler gauge can be moved smoothly between the reel andbedknife across the entire length of the reel and bedknife, such thatthere is only a slight drag of the feeler gauge as it is moved acrossthis length. To verify reel and bedknife sharpness and a correctreel-to-bedknife adjustment, a single strip of paper is often insertedbetween the reel blade and bedknife while the reel is turned forward byhand. If the reel cuts the paper, the sharpness and adjustment areusually determined to be correct. The quality of the cut of the piece ofpaper across the single sheet can be examined to indicate whether theclearance is correct.

Reel adjustments are also necessary when a cutting reel unit is“re-tasked,” in effect, adjusted for cutting another type of grass orgrass to be cut to a different height. For example, a cutting reel unitcould be re-tasked from an adjustment appropriate for a golf coursefairway to adjustment appropriate for a golf course green, the two areashaving different grass height requirements. However, re-tasking acutting reel unit is time-consuming. To avoid re-tasking cutting reelunit, many golf courses have cutting reel units or cutting machineswhich remain designated or pre-adjusted for particular grassrequirements, in effect, a designated group of cutting units fordifferent areas of the golf course. This technique necessitates multiplecutting units or cutting machines. Multiple cutting units or machinescan result in higher capital costs and maintenance costs.

The present inventors have recognized that the cut quality of a reelmower is largely determined by the accuracy and precision of adjustmentof several key factors. The present inventors have recognized thatproper mower adjustments are often hard to achieve through manualadjustment methods.

The present inventors have recognized that the reel-to-bedknifeadjustment is one such adjustment that needs to be adjusted accuratelyand precisely, but is often hard to achieve on individual mowing reels.The present inventors have recognized that the reel height-of-cutadjustment is another such adjustment that needs to be adjustedaccurately and precisely, but is also difficult to adjust on individualmowing reels.

The present inventors have recognized that the accuracy and precision ofthese adjustments can be improved through automated adjustments.

The present inventors have recognized that a need exists for dynamicadjustment capability for multi-area mowers or mowers that are capableof mowing multiple areas having different cutting requirements. Thepresent inventors recognize that a need exists to be able to re-task acutting reel unit dynamically to allow a single machine to mow multiplearea types with different cutting reel unit setup requirements.

The present inventors have recognized the need to also modulate reelspeed, to provide reel-to-bedknife contact detection, and to makecutting reel unit adjustments during operation of the cutting reel unit.

The present inventors have recognized the need to improve the adjustmentprocess to ensure a shorter required time, ease of adjustment, andimproved reel operation quality.

SUMMARY OF THE INVENTION

The invention provides a control system for adjusting the reel of acutting reel unit. The cutting reel unit can be carried by, or attachedto, a vehicle, such as a tractor, singularly or as one of a plurality ofcutting reel units, or can be incorporated into a riding mower, awalking mower or a ride-on mower, also singularly or as one of aplurality of cutting reel units.

The control system can control reel-to-bedknife clearance,height-of-cut, lateral leveling of the reel, and the reel rotationalspeed.

The cutting reel unit control system can be implemented through avariety of control architectures such as distributed control orcentralized control. The control protocol can be CAN, serial, or othercontrol protocols.

The cutting reel unit control system can be automaticallyself-adjusting, which periodically corrects the reel adjustments such asthe reel speed, the height-of-cut, the reel lateral leveling, and thereel-to-bedknife clearance, or corrects the reel to bedknife clearanceif contact between the reel and bedknife is sensed during operation.

The cutting reel unit control system can be configured as a centralcontroller or by controllers located at each cutting unit, or even by alocal controller designated for each actuator. The cutting reel unitcontrol system can be adjusted after operator or automatic initiation ofan adjustment routine in a central controller or by operator orautomatic initiation of control routines performed by controllers ateach cutting unit or at each actuator.

The cutting reel unit adjustment can be made by a controller external tothe cutting unit, such as by a control unit that is used in a shop tore-adjust or re-task a cutting unit for a pre-selected grass conditionor area and desired height-of-cut.

Alternatively to operator initiation, the cutting reel adjustments canalso be initiated by a controller or control units that is/areresponsive to a sensor such as a height of grass sensor, or by alocation sensor and/or sender on the cutting unit or cutting machinethat communicates with an external ground-based system or a globalpositioning system (GPS). These systems, responsive to externalconditions, along with the onboard control systems as described hereinfacilitate implementation of the control system in either a mannedcutting machine or an autonomous cutting machine.

For example, different areas of a golf course could be mappedelectronically and preprogrammed into the onboard or remote controllerand such controller could communicate with the external positioningsystem and thereafter adjust the actuators to adjust the cutting unitfor the type of grass, the area, and desired cut lines for correspondingareas of the golf course.

The apparatus of the invention includes a cutting reel, a framesupported on at least one support element that is supported on, and ismovable along, the ground, and a housing supporting the cutting reel,the housing movably mounted on the frame. A bedknife is carried on theframe. An actuator has a first portion connected to the frame and asecond portion connected to the housing, wherein a distance between thefirst and second portions is adjustable to set spacing between the reeland the bedknife, and including a motive mechanism that is activated toadjust the distance.

The cutting reel can be one driven in rotation by one or more hydraulicmotors, electric motors, by the traction drive of the mower machine orvehicle, or by other type drive.

Two actuators can be used, one actuator located at each end of the reel,and the actuators each have a first portion connected to the frame and asecond portion connected to one of two housings that support ends of thereel, wherein a distance between the first and second portions isadjustable, and including a motive mechanism that is activated to adjustthe distance.

According to another aspect of the invention, a control system for acutting reel unit includes a first frame; a second frame; a cutting reelsupported by the second frame; a bedknife arranged adjacent to thecutting reel and supported by the second frame; at least one supportelement arranged to translate along the ground and arranged to supportthe first frame; at least one first actuator connected between the firstframe and the second frame and arranged to adjust the relative elevationof the second frame with respect to the first frame; at least one secondactuator operatively connected between the reel and the second frame andarranged to adjust the clearance between the reel and the bedknife; anda controller signal-connected to the first and second actuators.

The control system can further comprise position sensors that aresignal-connected to the controller, the position sensors determining theprecise elevation of the reel with respect to the at least one supportelement and determining the position of the reel with respect to thebedknife.

The control system can include a sound detector arranged in closeproximity to the bedknife to detect touching between the cutting reelwhen spinning and the bedknife.

According to another aspect of the invention, an improved anti-backlasharrangement is provided for a linear actuator. The linear actuatorincludes a stepper motor that drives a lead screw that advances orretracts a rod from a housing. The anti-backlash arrangement includes ananti-backlash nut threaded on the lead screw and a spring. The spring isconnected to an end of the rod and to the anti-backlash nut. Theanti-backlash nut has a first surface abutting a second surface of therod, the spring pressing the first and second surfaces together suchthat thread play between the rod and the lead screw is removed. Thefirst and second surfaces are preferably conically shaped and nesttogether.

The disclosed invention provides advantages in that the apparatus andmethod allow for rapid and automatic adjustment of the reel-to-bedknifegap without operator intervention following operator initiation of theadjustment. The reel can be adjusted in seconds. The method has speedand consistency advantages over manual adjustment, and does not requiredetection of poor cut quality or excess surface wear in order to performthe automatic adjustment.

The disclosed invention provides advantages in that the apparatus andmethod allow for rapid and automatic adjustment of the height-of-cut ofa reel of a cutting reel unit without operator intervention followingoperator initiation of the adjustment. The reel can be adjusted inseconds. The method has speed and consistency advantages over manualadjustment, and does not require detection of poor cut quality in orderto perform the automatic adjustment.

By making these adjustments automatically, the reel adjustment processmay be accomplished more consistently without the presence of a skilledmechanic. The automated adjustment also provides the capability for thesupport of autonomous equipment.

The control system allows a cutting reel unit to be rapidly re-tasked tocut different grass heights for different areas of a golf course. Thesystem allows a single cutting reel unit to be readily usable formultiple golf course areas.

An adaptive threshold technique may be used to detect reel to bedknifecontact during a pre-adjustment analysis. The adaptive thresholdtechnique may include sampling each detector and analyzing the detectorsignal, setting detection threshold levels based on the signal levelabsent reel-to-bedknife contact, and detecting contact between the reeland bedknife by determining if the detector signal is inside or outsidea detection threshold window.

Numerous other advantages and features of the present invention will bebecome readily apparent from the following detailed description of theinvention and the embodiments thereof, from the claims and from theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a cutting reel unit according to theinvention;

FIG. 2 is a bottom perspective view of the cutting reel unit of FIG. 1;

FIG. 3 is a fragmentary sectional view taken generally along line 3-3 ofFIG. 1, with portions of the cutting unit removed for clarity ofdescription, with the reel pivoted away from the bedknife;

FIG. 3A is a schematic view of a reel position with respect to abedknife position;

FIG. 4 is a sectional view similar to FIG. 3 with portions removed forclarity of description with the reel pivoted toward the bedknife;

FIG. 5 is a sectional view of an actuator as shown in FIG. 3;

FIG. 6 is an enlarged fragmentary sectional view of a portion of theactuator shown in FIG. 5;

FIG. 7 is a bottom perspective view of the components shown in FIG. 4;

FIG. 8 is a side view of the cutting unit shown in FIG. 1 with portionsremoved for clarity of description wherein the reel is illustrated in anelevated operating position;

FIG. 9 is a side view of the unit shown in FIG. 1 wherein the reel isillustrated in a lowered operating position;

FIG. 10 is a fragmentary, partial sectional view taken generally alongoffset line 10-10 of FIG. 8;

FIG. 11 is a perspective view of the unit shown in FIG. 1 with the reelremoved for illustrating underlying parts;

FIG. 12 is a schematic diagram of a control system of the presentinvention;

FIG. 13 is a schematic block diagram illustrating a method according tothe present invention;

FIG. 14 is a fragmentary perspective view of an alternate embodimentwith portions of the cutting unit removed for clarity of description;and

FIG. 15 is a sectional view taken generally along line 15-15 of FIG. 14.

FIG. 16 is a schematic block diagram illustrating an adaptive thresholdtechnique for detecting reel-to-bedknife contact according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While this invention is susceptible of embodiment in many differentforms, there are shown in the drawings, and will be described herein indetail, specific embodiments thereof with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not intended to limit the inventionto the specific embodiments illustrated.

FIGS. 1 and 2 illustrate a mower cutting reel unit 10 according to thepresent invention. The mower cutting reel unit 10 is adapted to bepulled alone or within a group of like units by a vehicle such asdescribed in U.S. Pat. Nos. 5,343,680; 5,412,931 or 5,459,984, hereinincorporated by reference. A plurality of blades 11 are coupled togetherto form a generally cylindrical reel 12 which rotates about a transverseaxis in close proximity to an edge 14 a of a bedknife 14 (FIG. 2) forcutting vegetation, such as grass, with a scissoring action. A motor 16,carried at one side of a frame 18 that generally houses and supports thereel 12, drives the reel 12. The motor 16 can be a hydraulic, electricor other type motor. Alternatively, a transmission arrangement betweenthe traction drive of the machine or vehicle and the reel can be used torotate the reel. A hydraulic motor is indicated in the figures.

The inside frame 18 is carried by an outside frame 22. The outside frame22 is supported on front and rear rollers 24, 26 respectively. Theinside frame 18 is supported on the outside frame 22 by actuators 30, 32and by struts 36, 36. The struts 36, 36 are substantially mirror-imageidentical in configuration. A pushing or towing frame 42 is arrangedbetween the inner and outer frames 18, 22. The towing frame 42 includesvertical plates 44, 46 fastened to side plates 52, 54 of the outer frame22 by pins 56, 58 residing in slots 52 a, 54 a. The slots 52 a, 54 a arepart of a mechanism which permits the reel to be pushed from the rearwhen rolling, and still touch down heel first when lowered.

A crossbar 48 connects the side plates 44, 46. A vehicle connector orlift arm can be engaged at a select position along the crossbar 48 totow or push the cutting unit 10 along the ground during the cuttingoperation.

The outside frame 22 also includes adjustable bracket members 62, 62connected by fasteners 66 to a respective side plate 52, 54. The bracketmembers 62, 62 are substantially mirror-image identical inconfiguration. The bracket members 62, 62 each include a short L-shapedmember 62 a and a horizontal member 62 b. The members 62 a, 62 b includea series of holes 68 wherein a registered pair of holes between themembers is selectable to set a horizontal overall dimension of thebracket members 62, 62 using fasteners through the registered pair ofholes. The selectable dimension is useful where additional accessoriesare to be used, for example a conditioner, or a device that contacts andmanipulates the grass immediately before it is cut by the reel andbedknife, could be added to the unit 10 behind the roller 24. The unit10 is shown with holes 68 selected to set a maximum horizontal dimensionof the bracket members 62, 62 such as would be used when a conditioner(not shown) would be installed behind the front roller 24. With just thefront roller 24 used, different holes 68 would preferably be selected toset a minimum horizontal dimension of the bracket members 62, 62.Vertical portions 62 c, 62 c of the members 62, 62 extend downward to beconnected via plates 72, 72 to front support assemblies 76, 76 that aresupported by the front roller 24. The front support assemblies 76, 76are substantially mirror-image identical in configuration.

Plates 84, 84 connect the outer frame side plates 52, 52 to rear supportassemblies 88, 88 that are supported by ends of the rear roller 26. Therear support assemblies 88, 88 are substantially mirror-image identicalin configuration.

The inside frame 18 includes side plates 106,106 connected together bycrossbars 112, 114. The side plates 106,106 are substantiallymirror-image identical in configuration. A grass deflector plate 118 isarranged between the bars 112, 114 above the reel 12. The side plateseach include a front flange 122. A tube 126 is welded to each of thefront flanges 122. A tube 132 is also welded to each of the members 62b. Sleeve bearings 140 are fit into each tube and a pin, bolt or otherfastener 142 is used to pivotally connect each of the angled struts 36to a respective pair of tubes 126, 132.

FIG. 3 illustrates right side components of the unit 10. The left sidecomponents are configured in substantially the same, but mirror-imagemanner. The actuators 30, 32 each include a motor drive 30 a, a housing30 b, and an actuator rod 30 c extending out of a bottom of the housing30 b. The rod 30 c extends or retracts vertically from the housing 30 bby a selected turning direction of the motor drive 30 a. The housing 30b is fastened to the respective side plate 106 by fasteners 143. The rod30 c is pivotally fastened to the outer frame 22, particularly to therespective outer frame side plate 52 by a fastener or pin 146.

Thus, extension of the rods 30 c from the housings 30 b, of theactuators 30, 32, lifts the inside frame 18 with respect to the outsideframe 22. Retraction of the rod 30 c into the housing 30 b, of theactuators 30, 32, lowers the inside frame 18 with respect to the outsideframe 22.

The struts 36, 36 (FIGS. 1 and 2) prevents excessive forward or rearwardtipping of the inside frame 18 lifted or lowered at the rear thereof andensures a substantially straight vertical lifting or lowering of theinside frame 18. The geometry of the frames 18, 22, struts 36, 36 andactuators 30, 32 advantageously slightly tip the reel and bedknifeforward with rising height-of-cut. This change in the “angle of attack”results in a more effective cutting.

FIG. 3A illustrates schematically the side plate 106 and an outline ofthe reel 12 wherein the height-of-cut “h” from grade “g” and an offset“x” from the reel centerline “c” are shown. The attack angle “a” is alsoshown. Effective guideline maximum attack angles “a” with respect toheight-of-cut are:“h”=6 mm, “a”=0 deg“h”=20 mm, “a”<1.3 deg“h”=75 mm, “a”<5 degThe preferred embodiment of the invention satisfies these guidelines.

For the preferred embodiment, the table below sets forth the relativepositioning of the profile of the edge 14 a with respect to the reelcenterline “c” as the inside frame 18 is lifted through a range ofheight-of-cut “h” and tilted over a range on attack angles “a”.

“h” “a” “x” 10 mm 0.38 deg 6.95 mm 15 mm 0.81 deg 7.38 mm 20 mm 1.20 deg7.77 mm 25 mm 1.55 deg 8.12 mm 30 mm 1.86 deg 8.43 mm 35 mm 2.13 deg8.70 mm 40 mm 2.36 deg 8.93 mm 45 mm 2.56 deg 9.13 mm 50 mm 2.72 deg9.29 mm 55 mm 2.86 deg 9.43 mm 60 mm 2.95 deg 9.52 mm 65 mm 3.02 deg9.59 mm 70 mm 3.05 deg 9.62 mm 75 mm 3.06 deg 9.63 mm

Actuators 202, 204 are provided on a front side of the inside frame 18adjacent opposite ends of the reel 12. As illustrated in FIGS. 3 and 4,the actuators each include a motor actuator 202 a, a housing 202 b, andan actuator rod 202 c. The housing 202 b is fastened to the respectiveside plate 106 by fasteners 212. The rods 202 c, 202 c are fastened torespective reel bearing housings 216, 216 that journal the reel 12 atopposite ends of the inside frame 18. Each rod 202 c is pinned to a balljoint 220 that is fixed to the respective housing 216, by an elongatedpin 226.

Each reel bearing housing 216 is pinned to a respective side plate 106by a pin or fastener 230. The extension or retraction of the rods 202 c,202 c with respect to the housings 202 b, 202 b of the actuators 202,204, pivots the reel bearing housings 216, 216 about the pins orfasteners 230, 230. As illustrated in FIG. 4, by extending the rods 202c, 202 c and pivoting the reel housings 216, 216, the blades 11 can bebrought closer to or further from the bedknife 14 (FIG. 2),particularly, closer to or further from an edge 14 a of the bedknife 14.

Each ball joint 220 is carried on the base pin 231 (FIG. 10) that isfixed to the bearing housing 216 by being threaded tightly to thebearing housing using a thread-locking compound such as a LOCTITE®thread-locking product. The base pin 231 extends through the bearinghousing to slide through a slot 232 formed in the side plate 106. Foreach actuator 202, 204, an L-shaped spring 234 is fixed to the rod 202 cand presses against the ball joint 220 to bias the rod 202 c in thedownward direction, to remove play within the ball joint 220.

FIGS. 5 and 6 illustrate a typical actuator 30, 32, 202, 204 such as theactuator 202. The actuator 202 includes the motor drive 202 a, thehousing 202 b and the rod 202 c. Inside the housing 202 b there is adrive screw or lead screw 260 that is driven into rotation by a steppermotor 266 of the motor drive 202 a. The lead screw 260, being anextension of a motor shaft 268, is rotated by the stepper motor 266.

The rod 202 c is a substantially hollow cylinder and includes a rod endportion 274 fixed to a rod body portion 276 by threaded mutualengagement. The lead screw 260 extends substantially through the bodyportion 276. A lead nut 280 is fixed to the rod body portion 276. Thelead nut 280 can include an outer metal casing 282, such as brass, andan inner sleeve 284, such as plastic, having internal Acme threadsengaged to corresponding external Acme threads on the lead screw 260.The lead screw 260 can be stainless steel. Alternatively, the lead nutcould be formed as a unitary part with the rod body portion 276, such asboth being formed of plastic or metal.

An anti-backlash nut 288 is threaded onto the lead screw 260. Theanti-backlash nut 288 also includes Acme threads, preferably plastic,and engaged to the external threads of the lead screw 260. Theanti-backlash nut 288 includes a convex conical tapered surface 290which abuts a concave conical tapered surface 292 of the rod bodyportion 276 or the lead nut 286 fixed to the rod body portion 276.

A coil spring 296 surrounds the lead screw 260. The coil spring 296 isconnected to the anti-backlash nut at one end 296 a and to the rod endportion 274 at an opposite end 296 b.

The anti-backlash feature of the invention is provided by the resilientforce of the anti-backlash nut 288 urged in rotation around the leadscrew 260 by the spring 296, against the rod body portion 276 or leadnut 286. This force takes up all thread play between the lead screw 260threads and the lead nut 280 threads. The anti-backlash nut 276 and thelead nut 286 advance and retreat substantially together on the leadscrew 260.

The inclination of the surfaces 290, 292 increases the normal forcebetween the lead nut 280 and the anti-backlash nut 276 or the rod bodyportion 276, wherein the inclination is steeper than the inclination ofthe Acme threads of the anti-backlash nut 276 and lead screw 260. Thiscauses the anti-backlash nut 276 to press against the lead nut 280 orthe rod body portion 276 sufficiently to remove play in the engagedthreads, but will prevent the anti-backlash nut 276 and lead nut 280from tightening excessively on the lead screw 260.

The anti-backlash nut 288 and the spring 296 can be eliminated in theactuators 30, 32 where fine positioning accuracy is not required. Theanti-backlash feature is most advantageous for the actuators 202, 204where fine positioning accuracy is desired.

The motor drive 202 a includes windings 306, bearings 308, and anoptical encoder 310. The encoder 310 includes a target disk 312 and aread head 314. The read head 314 includes two spaced-apart lightemitting and reading devices, used to determine position of the rotatingtarget disk and also its direction of rotation. To set absolute positionof the rod, the rod can be extended or retracted by the stepper motor266 to maximum or minimum extension, until the motor 266 stalls. At thisposition, the encoder will send no more pulses to the controller sincethe target disk stops rotating. This sets the maximum extension ormaximum retraction. The stepper motor 266 can then be reversed andselectively driven a pre-selected amount to properly position the rodend portion 274.

FIGS. 7 through 9 and 11 illustrate further views of the unit 10 withdifferent components removed for clarity of description. FIG. 8illustrates the inside frame 18 in a lowered position with respect tothe outside frame 22. FIG. 9 illustrates the inside frame 18 in a raisedposition with respect to the outside frame 22. FIG. 9 illustrates adetector 320 (described below) mounted on a plate 298 and positionedadjacent to an end wall 14 b of the bedknife 14. An identical detector320 can be installed in mirror-image fashion to an opposite end wall ofthe bed knife.

FIG. 12 illustrates a controller 300, such as a microprocessor, used tocontrol the actuators 30, 32, 202, 204. An operator input station 306such as a keypad is provided for giving instructions to the controller300.

Alternatively, the cutting reel unit control system can be automaticallyself-adjusting, which periodically corrects the reel adjustments such asthe reel speed, the height-of-cut, the reel lateral leveling, and thereel-to-bedknife clearance, or corrects the reel to bedknife clearanceif contact between the reel and bedknife is sensed by the detector 320during operation.

The cutting reel unit control system can be configured as a centralcontroller or by controllers located at each cutting unit, or even by alocal controller designated for each actuator. The cutting reel unitcontrol system can be adjusted after operator or automatic initiation ofan adjustment routine in a central controller or by operator orautomatic initiation of control routines performed by controllers ateach cutting unit or at each actuator.

The cutting reel unit adjustment can be made by a controller external tothe cutting unit, such as by a control unit that is used in a shop tore-adjust or re-task a cutting unit for a pre-selected grass conditionor area and desired height-of-cut.

The cutting reel adjustment can also be initiated by the controllerresponsive to an external sensor such as a height of grass sensor, orresponsive to a location sensor and/or sender on the cutting unit orcutting machine that communicates with an external ground-based systemor a global positioning system (GPS). These systems, responsive toexternal conditions, along with the onboard control systems as describedherein facilitate implementation of the control system in either amanned cutting machine or an autonomous cutting machine.

The operator, via the input station 306, or the controller responsive toan automatic routine, can command the reel rotating speed and directionof rotation to the reel motor 16. The controller can be signal-connectedto a system 350 that controls the speed and direction of rotation of thereel motor 16 to adjust the speed and direction of rotation of the reel12. When a hydraulic motor is used, the system 350 can include speed anddirection of rotation control of a hydraulic pump 352 that drives thehydraulic motor and/or flow control of valving 354 that divertshydraulic fluid away from the motor 16 to adjust speed and/or reverseshydraulic fluid flow to change direction of rotation of the motor 16.The controller 300 can adjust the speed of the reel 12 based on grasslength or type of grass given operator or other input.

The operator, via the input station 306, or the controller responsive toan automatic routine, can command adjustment of the height-of-cut, sayin mm, and can command the automatic adjustment of the reel-to-bedknifeclearance. For adjusting the reel-to-bedknife gap as explained below, byoperator or automatic initiation the controller can command the reelmotor 16, such as via the system 350, to spin the reel 12 in a reversedirection before initiation of the adjustment procedure by the operator.The actuator pairs 30, 32; 202, 204 can be adjusted individually to seta desired lateral degree of either the height-of-cut level or thereel-to-bedknife clearance. A position signal S1 from each actuator readhead 314 is communicated to the controller 300, and an appropriate drivesignal S2 is sent to the stepper motor 266 of each actuator viaappropriate signal conditioning and/or amplification to position rod endportions 274 with respect to the respective actuator body 30 b, 202 b ofthe actuators 30, 32, 202, 204.

The detector 320 (FIGS. 2 and 9) can be used to adjust thereel-to-bedknife clearance. The detector 320 can be of a variety oftypes, including an accelerometer or a sound detector. The detector 320can be a sound detector such as a microphone, such as an EMKAY MR-3151from Emkay Innovative Products of Itasca, Ill., U.S.A. The microphonecan be potted in polyurethane for protection and to strain relieveassociated signal wires. The detector 320 can be provided in closeproximity to the bedknife 14. The detector 320, in the form of amicrophone, may be embedded in the bedknife, or mounted near thebedknife so as to detect the contact of the reel to the bedknife duringthe adjustment methods.

The detector 320 is signal-connected to the controller 300.Advantageously, during an adjustment procedure, the reel 12 is spunbackwards and the detector 320 detects and signals to the controller anycontact or “clicking” between the reel blades of the rotating reel 12and the bedknife 14. Preferably, two detectors 320, 320 are provided,one at each end wall 14 b of the bedknife, although a single detector320 could be used as well, located at a position where sound can bedetected from contact of the reel blades at either end of the bedknife.

According to one method, wherein the noise produced by the reel issensed by a microphone, or alternately by an accelerometer, theresulting vibration is analyzed to detect the presence or absence ofcontact.

The algorithm used to analyze the noise is designed to detect aparticularly prominent resonance point in the sensed sound when the reeland bedknife are clicking. The resonance is detected by using a singlefrequency range power spectral density (psd) estimate of the signalpower. The single range method calculates the psd at only a singlenarrow frequency range (or bin) of interest. Reducing the psd algorithmin this way significantly lessens the computational effort needed versusthe full psd. This style of algorithm is used to reduce sensitivity tospurious environmental noise. The resonance can also be detected inusing an analog or discrete switched capacitor narrow bandpass (ornotch) filter, rectifying the filter output, and then detecting the DClevel of the resulting signal.

Alternately, a simple algorithm that senses the increased noise levelwhen the reel/bedknife are in contact can be used, but this algorithmcan be sensitive to environmental noise.

A method of precisely positioning the reel 12 with respect to thebedknife 14 using the sound detector(s) 320 is set forth in FIG. 13. Themethods of the invention can all be automatically accomplished at thedirection of the controller after initiation by an operator. Althoughthe method as set forth below is described as being operator initiated,the method can also be initiated automatically during operation,initiated periodically by the controller or initiated by the sensing ofreel-to-bedknife contact during operation, or initiated by a change inreel tasking, i.e., a new type of grass or length of grass to be cut.This change in reel tasking can be initiated by a remote signal or asensed signal such as by a grass height sensor, or a ground-based or GPSbased position signal.

The steps of one method of the invention comprise:

1. registering adjustment mechanisms 202, 204 by moving the reeladjustment mechanisms 202, 204 to known positions, particularly, movingthe rods 202 c to known positions with respect to the bodies 202 b usingthe drive motors 202 a;

2. spinning the reel 12 in a reverse direction from the normal operatingdirection, normal operating direction being a counterclockwise directionas viewed in the right side view of FIG. 9, that is, during normaloperation the bottom of the reel 12 spins toward the bedknife;

3. moving the reel 12 toward the bedknife 14 an equal pre-selecteddistance on both ends of the reel, particularly by using the drivemotors 202 a to move the rods 202 c an equal pre-selected amount withrespect to the bodies 202 b;

4. moving the reel 12 toward the bedknife 14 on a first end of the reelby a continuous step or by incremental steps of the drive motor 202 a ofthe actuator 202 until a contact between the reel and the bedknife isdetected by the adjacent detector 320, particularly by using the drivemotor 202 a of the actuator 202 to extend the rod 202 c with respect tothe body 202 b; the contact can be detected as a faint clicking sounddetected by the detector 320 being in the form of a microphone;

5. moving the reel 12 on the first end of the reel away from thebedknife 14 to produce a clearance of a small pre-defined distance “y”,where y>desired gap width, particularly by using the drive motor 202 aof the actuator 202 to retract the rod 202 c with respect to the body202 b;

6. moving the reel 12 toward the bedknife 14 on an opposite end of thereel by a continuous step or by incremental steps of the drive motor 202a of the actuator 204 until a contact between the reel and the bedknife,a faint clicking, is detected by the adjacent sound detector 320,particularly by using the drive motor 202 a of the actuator 204 toextend the rod 202 c with respect to the body 202 b; the contact can bedetected as a faint clicking sound detected by the detector 320 being inthe form of a microphone;

7. moving the reel 12 on the opposite end of the reel away from thebedknife 14 to produce a clearance of the small pre-defined distance y,particularly by using the drive motor 202 a of the actuator 204 toretract the rod 202 c with respect to the body 202 b; and

8. repeating the adjustment of steps 4 through 7 “n” times wherein “n”is experimentally pre-determined to be the minimum number of cycles thatproduces the accurate pre-defined distance y on both ends of the reel.

Currently, it is anticipated that only a few cycles of steps 4 through7, such as n=3, will be needed to produce an accurate pre-defineddistance y on both ends of the reel. Alternately, the precise locationsof the first reel end with respect to the bedknife, at positions beforestep 4 and after step 5, and the precise locations of the respectivesecond reel end with respect to the bedknife, at positions before step 6and after step 7, can be stored and compared until a consistent distancey between the reel and the bedknife is achieved at each reel end. Theprecise locations are provided by the encoders 310 of the actuators 202,204 and sent to the controller.

9. after the accurate distance y is set at both ends of the reel, movingboth ends of the reel toward the bedknife by the difference between thepre-defined distance y and the pre-selected gap width, (y minus gapwidth) to set the pre-selected gap width between the reel and thebedknife. By first accurately setting the pre-selected reel-to-bedknifeclearance y as a penultimate setting, and then subsequently reducingthis clearance to the smaller gap width, the detection accuracy of themethod is enhanced because contact between the reel and bedknife duringthe click detection cycle is more likely to be limited to contact at theextreme ends of the reel. The resulting gap width between the reel andthe bedknife can be in the range of, but not limited to, about 0.001 to0.003 inches.

Other methods encompassed by the invention are possible. Method step 1above can be eliminated. Method step 2 can be modified wherein the reel12 is spun in the normal operating direction. Method step 3 can bemodified wherein the reel 12 is moved away from the bedknife 14 apre-selected distance on both ends of the reel. Method steps 5 and 7 canbe modified wherein the small pre-defined distance y can be equal to theactual gap width and method step 9 can then be eliminated.

Furthermore, although the steps refer to moving the reel toward or awayfrom the bedknife, this is to be interpreted as relative movement, suchrelative movement would also encompass moving the reel toward or awayfrom a stationary bedknife, moving the bedknife toward or away from astationary reel, or moving both reel and bedknife toward and away fromeach other.

FIGS. 14 and 15 illustrate an alternate embodiment spring assembly 400to replace the spring 234 shown in FIG. 3 and the anti-backlasharrangement, including the anti-backlash nut 288 and spring 296 shown inFIGS. 5 and 6. The actuator 202 is not shown in FIG. 14 but would beattached to the housing 216 in similar fashion as that shown in FIGS.3-7 and 10. The assembly 400 includes a hollow cylinder 402 fixed to theframe 106 by a clamp 406 fastened to the frame 106. The cylinder 402 hasan end wall 408. The cylinder 402 extends horizontally into a blind bore410 (FIG. 15) of a slider block 412. The cylinder 402 is open on an endwithin the blind bore 410. The coil spring 413 is captured within thebore 410, and braced against an end wall 414 of the bore and the endwall 408 of the cylinder. The slider block 412 has cylindrical pins orears 416, 418 formed with or attached thereto, extending from oppositelateral sides of the slider block 412.

A yoke 424 formed by pieces 424 a, 424 b pivotally captures the pins416, 418. The yoke 424 can pivot with respect to the slider block 412.The yoke 424 is fastened to an L-shaped arm 430. The L-shaped arm 430 isfastened by a bolt 440 to the reel bearing housing 216. The bolt 440 canbe replaced by an attachment that also includes the ball joint 220 shownin FIGS. 3 and 4 to also attach the actuator 202 at the same location.

In operation, the coil spring 413 exerts a force (to the left) on theslider block 412 that exerts a resilient downward force on the bolt 440and housing 216. Because of the geometry of the spring assembly 400, asubstantially constant resilient force is exerted on the bolt 440 andhousing 216 over a wide-angle of movement of the housing 216, pivotingabout the connection 230. The force applied to the bolt 440 and housing216 varies only a small amount even as the compression of the spring 413varies by a larger amount.

The assembly 440 eliminates backlash in the actuator and play in theball joint 220 allowing use of a less-precise actuator. Also, any impactloading on the reel can be largely absorbed by the spring, instead of bythe actuator.

FIG. 16 illustrates an adaptive threshold technique for detectingreel-to-bedknife contact during a pre-adjustment analysis of the reelcutting unit. The adaptive threshold technique may include stepsperformed by a microprocessor; i.e., a 16 bit microcontroller such as anInfineon C167. Detectors on which the adaptive threshold method may beused include sound detectors such as microphones embedded in adjustmentactuators, or other detectors that can detect reel-to-bedknife contact.The adaptive threshold technique may include sampling each detector oneor more times and analyzing the detector signal. The adaptive thresholdtechnique may be used to determine the signal level in the absence ofreel-to-bedknife contact, set detection threshold levels based on thesignal level absent reel-to-bedknife contact, and detect contact betweenthe reel and bedknife as the gap is adjusted by determining if thedetector signal is inside or outside the detection threshold window.

In one embodiment, the adaptive threshold technique may be used todetermine the condition of a detector. More specifically, the adaptivethreshold technique may be used to compare the noise obtained from thedetector with and without operating the adjustment actuator. Adifference in the noise between these two conditions indicates thedetector is in good condition and functioning properly. If there islittle or no difference in the noise, the detector may be in poorcondition and/or may not be functioning properly, and thereel-to-bedknife gap adjustment procedure may be aborted.

In one embodiment, the adaptive threshold technique may be used todetermine the level of ambient and/or background noise in the absence ofreel-to-bedknife contact, and may include one or more of theseparameters: average signal level, maximum signal level, and minimumsignal level. For example, if a sound detector or microphone is used,the average, maximum and minimum microphone voltages may be determinedwith the reel running backwards in the absence of reel-to-bedknifecontact. From these parameters, a threshold window may be set for thedetector between an upper detection threshold and lower detectionthreshold. For example, the threshold window may be set at levels plusand minus from the maximum and minimum signal levels, or a ratio of themaximum and minimum signal levels. In one embodiment, the thresholdwindow may be set at 1.5 times the difference between the maximum andaverage signal levels, and 1.5 times the difference between the minimumand average signal levels in the absence of reel-to-bedknife contact.

In one embodiment, the adaptive threshold technique may limit the widthof the threshold window set for each detector to ensure reel-to-bedknifecontact may be distinguished from other noise. If the width of thethreshold window for a detector exceeds a specified amount, the adaptivethreshold technique may: (a) select another detector embedded in anotheractuator on the cutting reel unit, and analyze the signal from thatdetector; (b) proceed with the reel-to-bedknife gap adjustmentprocedure; or (c) abort the adjustment.

In one embodiment, a reel-to-bedknife gap adjustment procedure mayinvolve using a linear actuator and/or motor to incrementally reduce thegap between the reel and bedknife. A microprocessor may be programmed tosample the detector signal at each increment or step. If the reel andbedknife come into contact, the detector signal should be outside thethreshold window. If the detector signal is outside the thresholdwindow, a controller may command the linear actuator and/or motor toreverse direction and increase the reel-to-bedknife gap to set a desiredfinal gap.

In one embodiment, the adaptive threshold technique may include multiplesamples of the detector signal for each increment (i.e., each step orpulse) of the actuator or motor. Additionally, a time dimension may beused in addition to a threshold window. A time dimension may indicatereel-to-bedknife contact only if the detector signal stays outside thethreshold window for at least a specified time period. For example, ifthe first sample is outside the window, one or more additional samplesmay be obtained before moving the actuator. Thus, the technique maydetermine if the detector signal persists outside the window.Alternatively, an integration technique may be used to determine if aplurality of samples are sufficiently outside the threshold window toestablish reel-to-bedknife contact. The adaptive threshold technique maydetermine the area under a curve once the detector signal is outside thethreshold window. With a time dimension, the adaptive thresholdtechnique may reduce or eliminate the possibility that random highfrequency signals from a detector will produce false positive signalswhile the reel and bedknife are not in contact. The time dimensioneffectively provides a digital low pass filter for the detector signal.

The adaptive threshold technique may be advantageous because it requiresvery little processing power based on the number of instructions neededto execute between samples, and minimizes processor requirements andcost as a result. Most of the signal analysis may be performed beforethe adjustment process begins. For example, pre-adjustment signalanalysis may involve several thousand or more samples to set thedetection threshold window, and as much as 20 seconds with a 16 bitmicroprocessor. During the adjustment process, after the thresholdwindow is set, high speed complex signal analysis is not required.Instead, simple summing and comparison operations on the sample valuesmay be performed in a few microseconds using, in many cases, a singleprocessor instruction.

Additionally, the adaptive threshold technique is fast. For example, thetechnique may require a minimal number of samples to determine if thereel and bedknife are in contact, before setting the finalreel-to-bedknife gap. Another advantage of the adaptive thresholdtechnique is that it can be performed on each detector before eachadjustment. If the detector does not pass the check, or the backgroundnoise level is excessive, the reel-to-bedknife adjustment procedure maybe aborted, or another detector may be used instead.

From the foregoing, it will be observed that numerous variations andmodifications may be effected without departing from the spirit andscope of the invention. It is to be understood that no limitation withrespect to the specific apparatus illustrated herein is intended orshould be inferred. It is, of course, intended to cover by the appendedclaims all such modifications as fall within the scope of the claims.

1. A method for detecting reel-to-bedknife contact of a reel cuttingunit, comprising the steps of: obtaining a plurality of signals from areel-to-bedknife contact detector to determine a background noise signallevel from the detector absent reel-to-bedknife contact; setting athreshold window higher than the background noise signal level; reducingthe gap repeatedly between the reel and bed knife and after eachreduction determining if a signal from the detector is outside thethreshold window; and discontinuing the gap reduction if the signal fromthe detector is outside the threshold window.
 2. The method of claim 1further comprising reducing the gap between the reel and bedknife inincrements.
 3. The method of claim 1 further comprising setting thethreshold window based on an average, maximum and minimum signal levelof the detector in the absence of reel-to-bedknife contact.
 4. Themethod of claim 1 wherein the threshold window is set between an upperdetection threshold and a lower detection threshold.
 5. The method ofclaim 1 further comprising determining if the threshold window exceeds aspecified amount.
 6. The method of claim 1 further comprisingdetermining if there is any difference in detector noise with andwithout the adjustment actuator operating.
 7. The method of claim 1further comprising reducing the gap repeatedly until the signal from thedetector is outside the threshold window for at least a specified timeperiod.